This kind of error we got before

The scenario was the
1)shared memory segment created while the database startup(SGA) didn't have permissions properly .Actually it was created with different userid than oracle owner.

2)the above thing is due to the file permission
$ORACLE_HOME/bin/oracle has got changed
ideally the permission should be 6751


In above situations we got ORA-1005

make sure that your application uses proper listener etc..
request should come thru listener etc...


GOOD LUCK